Cold-workable permanent magnet alloy

ABSTRACT

A PERMANENT MAGNET ALLOY MAINLY CONTAINING CO, NI, CR AND FE AND HAVING A REPLACEMENT RELATION BETWEEN CO AND NI OF CO WT. PERCENT=50-2.5(NI WT. PERCENT)-531.5(NI WT. PERCENT), WHICH CAN VERY EASILY BE SUBJECTED TO MECHANICAL WORKING AND COLD WORKING AND YET IS VERY CHEAP OWING TO THE PRESENCE OF LESS THAN 1% BY WEIGHT OF V CONTARY TO VICALLOY CONTAINING 10-14% BY WEIGHT OF V.

June 27, 1972 JIRO MATSUMO TO ET 3,673,010

COLD-WORKABLE PERMANENT MAGNET ALLOY 4 Sheets-Sheet 1 Original Filed May 15, 1967 38:00 E 3 321 6282 m w Per Cent Chromium in ze'bcobalt-lo'nNickellron' INVENTOR S J/eo M/47'JUM070 1 041 Jin/aazu ymv r JWN v ATTORNEYS June 27, 1972 Original Filed May 15, 1967 Per Cent Cobalt, Chromium JIRO MATSUMOTO ETAL COLD-WORKABLE PERMANENT MAGNET ALLOY' 4 Sheets-Sheet Fig. 2

Per Cent Nickel INVENTORS Jneo MfifSl/MOTG Mn-mrasm rqxzucw/ fll/M/CH/ 4a: How SEA/60x0 BY W ATTORNEYS June 27, 1972 JIRO MATSUMOTO COLD-WORKABLE PERMANENT MAGNET ALLOY Original Filed May 15. 1967 Field SfrenqthJ-i,

in Oersteds I 4 Sheets-Sheet 5 lnduction,8, in Gausses INVENTORS gm? *JM ATTORNEYS June 27, 1972 ||RQ MATSUMOTO ETAL 3,673,010

COLD-WORKABLE PERMANENT MAGNET ALLOY Original Filed May 15, 19s? 4 Sheets-Sheet 4 Fig. 4

Induction B in Gausses -4oo- -3oo -2oo -m o Field Strenq h H in Oersjeds INVENTORS JIRO Man-aware Km SEA/604:0

ATTORNEYS United States Patent Office 3,673,010 Patented June 27, 1972 ABSTRACT OF THE DISCLOSURE A permanent magnet alloy mainly containing Co, Ni, Cr and Fe and having a replacement relation between Co and Ni of Co wt. percent=50-2.5(Ni wt. percent)-53- 1.5 (Ni wt. percent), which can very easily be subjected to mechanical working and cold working and yet is very cheap owing to the presence of less than 1% by weight of V contrary to Vicalloy containing -14% by weight of V. i

This application is a continuation of application Ser. No. 638,199, filed May 15, 1967, now abandoned.

The inventors paid attention to the a+'y two-phase field of FeCo-Ni system alloy and after elaborate experiments have found out that if a suitable amount of Cr, Mo, V etc.: are added to the Fe-Co-Ni system alloy, a series of permanent magnet materials each having an excellent workability and magnetic characteristics comparable with those of Vicalloy can be obtained in a less expensive manner.

For a better understanding of the invention reference is taken to the accompanying drawings, in which:

FIG. 1 shows curves illustrating relations between CI content of the permanent magnet according to the inventiorr and magnetic characteristics thereof;

FIG. 2 is a diagram showing ranges covered by compositions Co, Ni and Cr of the permanent magnet according-to the invention; and

FIGS. 3 and 4 are demagnetization curves of the permanent magnets according to the invention.

The invention will now be explained with reference to examples of permanent magnet alloy embodying the invention.

Compositions, magnetic characteristics and aging temperatures of some samples of Fe-Co-Ni-Cr system alloy according to the invention are listed in the following Table 1.

TABLE 1 Coercive Residual Aging 0 Co Ni Cr force induction tempera- (pereent) (percent) (percent) (percent) Bic (0a.) Br (G) ture 0.)

Sample Number:

The present invention relates to a permanent magnet alloy which can be subjected to mechanical working and cold working in an extremely easy manner and is less expensive.

Vicalloy has been worked into a wire, a thin plate etc. and used as permanent'magnet materials for measuring instruments. The use of the Vicalloy has recently been remarkably extended into the field of a semistationary memory, a hysteresis motor etc. in accordance with development of the automatic control technics.

Vicalloy is a permanent magnet material transformed into a phase by quenching and cold working and hence subjected to aging at the (1+7 two-phase field to precipitate 7 phase in the matrix of a phase and thus become magnetically hardened.

However, Vicalloy contains 50-52% by weight of Co and 10-14% by weight of V so that it has disadvantage of considerable expense.

The principal object of the invention is to obviate the above disadvantages of Vicalloy and provide a permanent magnet alloy which can very easily be subjected to mechanical working and cold working and yet is very cheap.

In order to obtain the samples having the magnetic characteristics shown in the above Table 1, 5 kg. of an ingot melted in air was subjected to hot forging and rolling treatments and then quenched from a temperature of 85. 0-l050 C. and subsequently aged at a temperature of 500-650 C. As can be seen from the Table 1, it is important that the magnet alloy according to the invention has a given composition ratio between Co, Ni arid Cr. N

The inventors have experimentally ascertained that the composition ratio between Co and Ni of the magnet alloy according to the invention can be given by the following formula.

Co Wt. percent=502.5 (Ni wt. percent)- 53-l.5 (Ni wt. percent) of the alloy becomes rapidly decreased until the alloy Compositions, magnetic characteristicsand aging temperatures of further samples of Fe-Co-Ni-Cr system alloyaccording to the invention wherein a part or all of Cr is replaced by Mo and/or V are listed in the following with the above formula showing the relation between Co Table 3.

TABLE 3 Coercive Residual Aging tem- Co Ni Cr Mo force induction pereture Sample No. (percent) (percent) (percent) (percent) (percent) Hc (oe.) Br (G) C.)

and Ni and hence decrease the amount of Cr as shown in FIG. 2.

The magnet alloy according to the invention comprising 1542% by weight of Co, 516% by weight of Ni and 3-9% by weight of Cr as shown by shaded areas in FIG. 2 showed particularly excellent magnetic character- 'istics.

Moreover, the inventors have experimentally ascertained that the magnet alloy according to the invention added with a small amount of Mo, V etc. can improve the magnetic characteristics thereof, and that a part or all of Cr may be replaced by Mo, V etc.

Compositions, magnetic characteristics and aging temperatures of other samples of Fe-Co-Ni-Cr system alloy according to the invention wherein a part or all of Cr is replaced by Mo are listed in the following Table 2.

The samples shown in the Table 3 were obtained after quenched from 950 C. and subsequently aged at a temperature of 550-560-C.

Replacement of Or by Mo and/or V causes to increase the residual induction (Br) of the alloy, but causes to decrease the coercive force (He) of the alloy in the same manner as in the case of replacement of Cr by M0 only. Even if all of Cr is replaced by Mo and V, the alloy still reserves more than 100 0c. of the coercive force (He). Thus, it is possible to'replace all of Cr by Mo and/or V.

Both Mo and V are very expensive if compared with Cr so that it is desirable to make the amount of Mo and V to be added as small as possible.

In the permanent magnet alloy according to the invention, C is a considerably distrubing element capable of deteriorating the workability, decreasing the coercive TABLE 2 Coercive Residual Aging tem- C (per- Co (per- Ni (per- Cr (per- Mo (perforce He induction peratnre cent) cent) cent) cent) cent) (oe.) Br (G) C.)

The samples shown in the Table 2 were obtained after quenched from 950 C(and subsequently aged at a temperature of 550660 C. r Addition up to 1% by weight Mo to the Fe-Co-Ni-Cr system alloy according to the invention is very effective. But, it is not desirable to add more than 2% by weight of Mo because such amount of Mo causes to decrease the residual induction (Br) of the alloy. Replacement of Cr by Mo causes to increase the residual induction (Br) of the alloy, but causes to decrease the coercive force (He) of the alloy. Thus, it is desirable to replace less than 4% by weight of Cr by M0.

The samples having excellent magnetic characteristics force (He) and also conspicously decreasing the residual induction (Br). Thus, it is desirable to use less than 0.05% tion, C is a considerably disturbing element capable of by weight of C, but 0.1% by weight of C is permissible. The inventors have also found out that addition of Ti, Zr, Nb to the alloy according to the invention is effective in a certain degree to obviate the above bad influences of C. These elements, however, serve to somewhat increase the coercive force (He) of the alloy according to the invention, but decrease the residual inductio (Br).

Compositions and magnetic characteristics of still other samples of Fe-Co-Ni-Cr system alloy according to the invention wherein Ti is added are listed in the followshown in the Table 2 also satisfy the above mentioned ing Table 4.

TABLE 4 Coercive Residual 0 Co Ni Cr Mo Ti force He induction Sample No. (percent) (percent) (percent) (percent) (percent) (percent) (oe.) Br (G) formula showing the mutual relation between the amount of Co and the amount of Ni of the alloy according to the invention.

5 perature of 600 C.

Addition of large amount of Ti causes to deteriorate the workability of the alloy according to the invention so that it is desirable to add less than 1% by weight of Ti.

Si, Al, Mn etc. are added as a deoxidizer to the alloy according to the invention, but these elements added serve to decrease the residual induction (Br) and also deterio rate the workability thereof. Thus, it is necessary to add less than 1% by weight of these elements, but less than 0.6% by weight of both Si and Mn and less than 0.2% by weight of A1 are the most desirable range to be added to the alloy according to the invention.

In accordance with the invention elements such as B, Zr, Nb, Ca, Mg etc. may be added to the alloy for the purpose of improving the workability of the alloy. The inventors have found out that less than 1% by weight of one of these elements is efiective to improve the workability of the alloy according to the invention without deteriorating the magnetic characteristics thereof. As wellknown in the art, addition of small amount of S, Se, Pb to the alloy according to the invention makes it possible to improve the mechanical workability of the alloy.

The magnet alloy according to the invention is capable of further improving the magnetic characteristics thereof if it is subjected to cold working. That is, the magnet alloy according to the invention subjected to hot working may be quenched from 7 phase field. Then, the alloy is subjected to pickling treatment to remove scales from the alloy and subjected to drawing and rolling treatments at room temperature. Subsequently, the alloy is aged at a temperature of 500-650 C. for suitable hours thus improving the magnetic characteristics. The cold working causes to somewhat decrease the coercive force (He) of the alloy, but remarkably increase the residual induction (Br) thus considerably improving the maximum energy product.

The samples 26-30 shown in the Table 3 are subjected to hot rolling treatment and then subjected to pickling treatment and subsequently subjected to 70% of cold rolling. The samples thus treated are aged at a temperature of 600 C. for 1 hour. The magnetic characteristics of the samples thus cold worked are shown in the following Table 5.

10 550 C. for 1 hour.

FIG. 4 shows demagnetization curves of the magnet alloys according to the invention which were subjected to 70% cold rolling and subsequently aged at a temperature of 600 C. for 1 hour. The curve C shows the demagnetization curve 0 fthe sample' No. 26 and the curve D shows the demagnetization curve of the sample No. 30.

As above explained with reference to the examples, the magnet alloy according to the invention is comparable with Vicalloy in the magnetic characteristics and workability, but is less expensive than Vicalloy as the magnet alloy according to the invention contains lesser amount of Co and V.

The magnetic characteristics of the magnet alloy according to the invention can be adjusted for a wide range by changing conditions required for components, heat treatments or working processes etc., so that the invention renders it possible to manufacture in an easy manner magnet alloys having magnetic characteristics suitable for a semistationary memory, ferreed or hysteresis motor etc.

We claim:

1. A cold-workable permanent magnet alloy in the form of gamma phase precipitated in a matrix of alpha phase, characterized by a high coercive force of at least about oersteds, consisting essentially of 15 to 42% by 3 weight of Co, 5 to 16% by weight of Ni, the Co and Ni being related to each other by the equation Co wt. percent=(502.5 (Ni wt. percent) to (53-1.5 (Ni wt. percent) 3 to 9 by weight of Cr, not more than 2% by weight of Mo, not more than 1% by weight of V, not more than 0.1% by weight of C, not more than 1% by weight of Si, not more than 1% by weight of Mn, not more than 1% by weight of A1, and not more than 1% TABLE 5 Coercive Residual 0 Co Ni Cr 0 V force He induction Sample No (percent) (percent) (percent) (percent) (percent) (percent) (0a.) Br (G) The values of the residual induction '(Br) shown in the Table 5 become remarkable increased if compared with those shown in the Table 3. In case of carrying out the by weight of a member selected from the group consisting of Ti, Nb, Zr and a mixture thereof, balance essentially Fe.

References Cited UNITED STATES PATENTS OTHER REFERENCES The Alloys of Iron and Nickel, Marsh, 'McGraw-Hill Book Co., Inc., New York, N.Y., 1938, pp. 269-273 and Bozorth, Ferromagnesium, D. Van Nostrand Co., Inc., New York, 1951, pp. l69.

CHARLES N. LOVELL, Primary Examiner ='U.S. Cl. X.R. 

